If you're set on visiting dublin castle, the self-guided version leaves most people confused. Empty rooms with wall plaques about medieval foundations and british rule.

Guided tour costs extra €8 but actually explains why place matters instead of letting you wander around lost. Guides bring the history alive. Chester beatty library same complex, free, more interesting than basic castle rooms anyway.

Honestly though, plenty better things in dublin if you're not particularly interested in castle history.